Fuse



May 27, 1941. H. A. TRIPLETT FUSE Filed May 26, 1937 4-Sheets-Sheet 1May 27, 1941; -H. A TRIPLETT FUSE Filed lay 26. 193'? 4 Sheets-Sheet 2May 27, 1941. H. A. TRIPLETT FUSE Filed May 26, 1937 4 Sheets-Sheet 3May 27, 1941. H. A. TRIPLETT 2,243,135

FUSE

Filed may ze, 1957 4 sheets-sheet 4 @if ,gg- /00 /06 /07 [0g //3 /0/ lf2l fr, l@ u l y--/ l* 6 l )U3 /01 J/LVHP (HELE Hue I l /05 ll .Y QQ /02Il? Qv/l//fl /f/ v v /H- W' Jr lla "/g current therethrough.

"Planted Map2?, 194i amiss rosa nigga. Triple, wnmmani., um u porationof Delaware oagiallbaeor-` Anuman my ze, 1m, sensi No. mass (ci.:bo-113s) '44 claims.

I My invention relates, generally,` to fuse devices and it hasparticular relation to the construction of fuse links that are intendedto be replaced once they have blown. It is further particularly relatedto the construction of fuse links that are l especially adapted. for usein the secondary or low voltage. high current, circuit of a distributiontransformer, although their use is not limlted to this application.

'I'he thermal duty to which a fuse device in the secondary or lowvoltage, high current, circuit of a distribution transformer issubjected is considerably greater than the thermal duty imposed'on afuse device inthe primary or high voltage. low current, circuit of thetransforrner. This difference in thermal duty is caused by therequirement that the fuse device in the secondary circuit protect thetransformer during overload and clear the circuit during overload orshort circuit without blowing the primary fuse. 'Thus it must operateclose to its minimum.` fusing cur-` rent without deterioration.

The object of myinventlon, generally stated, is'to p\ovide a fuse linkthat will operate under the foregoing conditions and which may bereadily and economically manufactured and installed.

An object of my invention is to provide for constructing a fuse link invsuch manner that it will operate close to its minimum fusing current ata relatively low temperature with little heat dissipation or watt lossand, at .the same time, will not deteriorate because of flowing ofmetal, oxidation and the like.

A further object of my/invention is to increase the resistance of a fuseelement on ow of predetermined current therethrough by the interaction.of two or more metals forming the element in such manner that therupturing of th element is accelerated. l

Another object of my invention is to take advantage of the alloyingcharacteristics of two metals such as silver andl tin, to effect theinterruptlon of a circuit on flow of predetermined Still `another objectof my invention is to provide a composite fusible element having asheath formed of a metal having a relatively high conductlvity enclosinga core formed of a metal having a lower conductivity.

A specific object of my invention is to provide acomposite fusibleelement having a tin core and a silver sheath.

' Anothfl'object of my invention is to provide for electrical connectionto a composite fusible element comprising a. core formed of metal havlnga. relatively low melting point and a surrounding sheath formed of ametal having a relatively high melting point in such manner that heatgenerated in the core is rapidly conducted away from it.

Still another object of my invention is to p vide for interconnecting ametal sheathed fusible element and a stranded conductor in which thecross-sectional area of .the latter is not limited 'Another object of myinvention is to provide a readily replaceable fuse link construction em--ploying-a pair of terminals adapted to be biased -apart andinterconnected by a strain element and composite fusible element formedby, a'

low melting point core and a highvmelting point sheath.

Other objects of my invention will, in part, be obvious and in partappear hereinafter.

Accordingly, my invention is disclosed in the embodiments hereof shownin the accompanying drawings, and it comprises .the features ofconstruction, combinationof elements and arrangement of parts which willbe exemplied in the constructions hereinafter set forth, and the scopeof the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention reference may be had to the following detailed descriptiontaken in conjunction with the accompanying drawings,

. in which:

v ing a different length of core.

Figure 3 is a sectional view, at an enlarged scale, taken along the line'3 3 of Figure 2;

Figure 4 is a view, in front elevation, of another embodiment of a fuselink constructed in accordance with my invention, a portion being shownin section;

Figure is a sectional viewtaken along the line 5 5 of Figure 4;

Figure 6 is a view, partly in front elevation and partly in section,illustrating another embodiment of my invention;

Figure 7 is a sectional view taken along the line 4'l---l of Figure 6;

Figure 8 is a view, in side elevation, of a fuse housing in which thefuse links shown in the preceding figures may be positioned;

Figure 9 is a longitudinal sectional view taken along the line 9-9 ofFigure 8;

Figure 10 is a detail cross-sectional view taken along the line l-Ill ofFigure 9;

Figure 11 is a. detail sectional View taken along the line II-II ofFigure 9;

Figure 12 is a fragmentary sectional view of a fuse device of the liquidarc extinguishing ty-pe in which another embodiment of the presentinven-tion is employed;

Figure 13 is a sectional view, at an enlarged scale; taken along theline i3-I3 of Figure 12; Figure 14 is a view, at an enlarged scale, ofthe composite fusible element shown in Figure 12, the sheath being shownin section and the remaining parts being shown in elevation;

Figure 15 is a longitudinal sectional view of a replaceable fuse linkemploying a strain element and a composite fusible element;

Figure 16 is a sectional view, at an enlarged scale, taken along theline I S-IS of Figure 15; and

Figure-17 is a sectional view, at an enlarged scale, taken along theline I1-I1 of Figure 15.

Referring now particularly to Figure 1 of the drawings, it will `beobserved that the reference character l5 designates, generally, a fuselink which includes a composite fusible element shown generally at i6,to .which flexible conductors I1, in the form of a plurality of strandsof wire, are connected. It will be understood that the flexibleconductors I1 may be connected to suitable circuit terminals in thecircuit in which the fuse link l5 is connected for projecting the same.The composite fusible element I6 comprises a core i8 and a sheath orsleeve I3. 'I'he core I8 is composed of a metal having a relatively lowmelting point, such as tin, while the sheath or sleeve I9 is composedprincipally of 'a metal having a relatively high melting poin't, such assilver.

'Ihe action on blowing of the composite fusible `element I6, formed oftwo distinct metals such as silver and vtin which are capable ofalloying with each other, is entirely different from that which takesplace when a fusible element is formed entirely of metal, such assilver, tin, lead, zinc or aluminum or alloys of A these or othermetals. When suiiicient current flows through a fusible element of thelatter type to heat it to its melting point, the metal passes from thesolid to the liquid state and, while the heat of fusion is beingapplied, the temperature renains substantially constant. Since the metalis in the liquid state and unrestrained, it flows away from its solidstate position or is vaporized by the heat of the resulting arc andopens the circuit. This action takes place at'a rate depending solelyupon the heat generated in the fusible element for a given set ofoperating conditions.

When sufficient current flows through a composite fusible element underthis same set of operating conditions to raise its temperature to themelting point of the lower of the two metals forming it, analloyingaction begins to take place. Since the melting point of the alloy thusformed is lower than that of eithery of the two metals, the change fromthe solid to the liquid state is accelerated. Moreover, since theresistance of the alloy formed is greater than the comblned resistanceof the two metals in the solid state, the change is further acceleratedfor the reason that the heat generated in the fusible element is afunction of its resistance. Once the alloying action sets in, the changeof a portion at least of the fusible element from the solid to theliquid state takes place with extreme rapidity due to vchanges in thesetwo factors, namely, melting point and resistance. At the same time,

until the melting point of the lower of the two metals is reached,substantially no change takes place. With a'proper proportioning of therelative amounts of the two metals forming the composite fusible elementI6, it is possible to provide a fusible element the characteristics ofwhich will remain unchanged until it is heated to the tem- -perature atwhich the lower melting point metal melts. At this definite point thechange from the solid to the liquid state begins to take place and,because of the lowering of the melting point of the resulting alloy andthe increase in its 'resistance, the action is somewhat cumulative andpositive circuit interruption takes place. It is then possible to moreaccurately predict the conditions under which a composite fusibleelement, such as a silver sheathed tin element, will lblow than is thecase when the element is formed of a metal such as pure tin for example.

In the design of fusible elements it is necessary not only to considerthe current at which an element will blow when it is heated to fusiontemperature for the first time but also it is necessary to consider theoperating characteristics of the ,element after it has once been heatednearly to the melting point, such as may occur as a result oftransients,`short time overloads and the llke,`

and then the temperature of the element decreases so that, at that time,it does not blow.y Under such conditions there may be a change in thecrystal structure of the metal as well as a change in its physicalappearance.

Considering, for example, a fusible element formed of pure tin, it hasbeen found that it will conduct a certain overload for a given timewithout blowing but the application of the same overload -conditions forthe same time subsequently may cause it to blow. 'Ihis somewhatinconsistent action Inay be attributed to the fact that the tin fusibleelement is necked down or somewhat reduced in cross section intermediateits ends because of its having been heated to a temperature approachingits melting point so that the same cross-sectional area is not availablefor conducting current as was previously the case. With such a fusibleelement it is not possible to accurately predict just when it will blowunder substantially all operating conditions. When the composite fusibleelement I6 is employed, this necking down action cannot take place forthe reasonthat the tin core I8 is restrained by the surrounding sheathor sleeve Il of silver.- However, as soon as the fusible element I6 isheated to a temperature that is sufficient to initiate the melting ofthe tin core IB, the alloying action takes place with the accompanyingincrease in resistance and the circuit is positively opened withoutdelay.

The action of a fusible element of the prior art, such as an elementcomposed of silver, tin,

and conductor I1. respectively, to

to the rapid change from the solid to the liquid state of the compositefusible element, while the other ball rolls along a dat surfacecorrespond-f ing to'the relatively slow change from the solid l to theliquid state of the fusible elements of `the mm-1mmimisitinsminiman.`nwinusw.

dersfcod that a fusible element composed entirelyof silver will operateat a,relatively bieb temperaturewhenitiscalledupontocarrycurrent forappreciable lengths of time close to the minimum fusing current. Bycombining the characteristics of tin andsilver it'is possible to takeadvantage ot the low temperature at which the composite fusible elementi. will operate over sustained-periods ol current now close to theminimum fusing-current snd,.at the same time, to obtain thedurabilitcharacteristic ofA silver because of its non-deterioratingability.

As'shown in ligure 1 of the drawings, the endsv 0 2l of the sleeve 'orsheath ii extend well beyond the ends 21 of the core Il.- The ends I!oi' the flexible conducwrs i1 mens inw un ends il of thesleeve orsheathil-and into abutting relation withthe ends 2i of thecore i8. The endsllofthesleeveorshesth llarethen illustratedmntotheends 2i and!! the sametherein. Since the ends!! of the nexible conductors II are readilydeformable. they arewellsuite'diorthepurposeofnllingtheends,zeonnesleeveonham lstcproviseeieetrien connection thereto and toconduct heat away from the core il.- y With a view to improving theconnection lie-i connectingsleevesllsevetoreinforcetheends not thesleeve or sheath il, particularly atelevatedtemperatureaandtoholdthesameintight fitting engagement with theends I2 o! the nexible conductors I1.

i It will bel understood that the several parts formingthefuselinkllmaybeotdiiferentrelative sise than illustrated in the drawings. Porthe construction of a fuse link for one particular rating the followingdimensions and materials were employed. The core Il may be composed oi'pure tin wire 1%" long and having a'diameter of .107". 'I'he sleeve orsheath Il may be composed of pure silver tubing having a length oi' 2%1'side diameter of .148". copper sleeves Il are 9S" long. while the bleconductors ll may be of any suitable length, for example, 3" long. Testshave indicated that the temperature of the sheath Il oi' a fuse linkhaving these dimensions will be about250" C. iustprior to blowing. It ispointed out that these figuresare by way of illustration only and arenot to be con-l strued as in any way limiting the proportions in whichthe various elements may be employed.

Because of the presence of the low melting pointcore ilthefuselinkilwilloperateata relatively low temperature even though it iscalled upon to conduct current in an amount that is close to the minimumfusing current. It is then possible' to provide a suitable housing forthe fuse link Il in close proximity thereto which will not be subjectedto a relatively high temperature,

such as the temperature that obtains when a fuse link formed solely ofsilver is operated close to its minimum-fusing current. K In Figure 2 ofthe` drawings another embodiment of the invention isillustrated. Thefuse linkii'thereshownissimilartothefuselink' Il shown in Figure 1.However, the core Il is relatively somewhat the nexible conductors Ilextend well within the sleeve or sheath il and beyond the deformed endsthereof.v This construction is desirable for two reasons. Hrst, it isunnecessary to deform the solid tin forming the core, as is the case inthe rconstruction ahem in Figure 1. Second, the heat that is gencratedinthe tin core il ismore readily. conducted away since the nexibleconductors i'l are formed of strands of copper and are. therefore.capable of conducting heat much more'readily than is tin.

f -It will be understood that the length oi the tween the compositefusible element il and the iieble' conductors I1, tubular connectors 2lin the ion of copper sleeves may be positioned are formed oi' alloymetal rather than pure metal,

aroundtheendslloithesl'eeveorsheathl.

low melting 'point core relative to the length maybedesired.Itwillalsobelmdel'stomzlthat l'br example, copper may be employedorsleeveaudthecoremaybe formed oi bismuth Aso the core may be formes ofsincor'lead or other like metals. It is not intended to limit thisinvention to the use of pure metals for the core and sheath. Either orboth of these members may be formed of suitable alloys 'as may be foundto be desirable.

While the present inventionis concerned pri- It will now be apparentthat I have provided and deformed therewith, as shown. The tubular `'H5a new method of opening an electric circuit on and an inside diameter of.128" and an outl shorter vand the ends 22 of the high melting pointsheath may be varied well as therelative cross-sectional areas, ss-

metals thanmilvcr .and tin may be em,

i (2) Forming an alloy having a melting point lower than that of thelower melting point metal, thereby accelerating the change of a portionof the fusible elemen-t from the solid tothe liquid state; and

(3) At the same time increasing the resistance of the fusible element,due to the formation of the alloy,.to further accelerate the change instate by the generation of additional heat.

By varying the relative cross-sectional areas of the core and sheath orsleeve, by varying the relative lengths thereof, and by varying theheatconducting capacitybetween the core and the terminals, it is possible toprovide a wide variety of fusible elements the operatingchar-acteristics of which can be accuratelyv predetermined. Such fusibleelements may be applied in circuits where highly selective action isrequired between two or more fuse devices connected in series circuitrelation, depending upon the' particular point a-t which the f-aultoccurs or at which the overload occurs that requires the circuit to beinterrupted.

In Figures 4 and 5'of 'the'drawings another then flattened, as shown, toprovide the desired connection.

It will'be observed that the intermediate portions 34 between the ends32 and 33 of the terminal connectors 3l form closures for the drilledapertures in the ends 33. These closures prevent the escape of the coremetal 28. If desired. the core 28` may be substantially shorter than thesleeve or sheath 29, as shown in Figure 2 for example, and the ends ofthe sleeve or sheath may be filled with conducting material, such asstrands of copper wire as will herein-after appear, to conduct heat awayfrom the core 2B for the purpose of increasing the rating of the link aswell as for other purposes which will also be set forth.

With a view to protecting the composite fusible element from injurywhile it is being handled and carried about, the construction shown inFigures 6 and '1 of the drawings may be employed. As there shown, a fuselink 31 is provided havingL terminal connectors 38 that are arranged tointerconnect a composite'fusible element, shown generally at 39 andcomprising a low melting point core 40 and a high melting point sleeveor sheath 4| formed of tin and silver, respectively, for the reasons setforth hereinbefore, and flexible conductors 42. Intermedil ate the endsof the terminal connectors 38 will be noted that the sleeve 44completely enembodiment of the invention is illustrated. The p closesthe composite fusible element 39 and-there-- by serves to protect itfrom injury during handling thereof. vIn addition, the sleeve 44, whencomposed of a material .such as fiber, serves to evolve larcextinguishing gases, on the occurmelting p oint, such as silver. Thesemetals are 4Circuit connections are provided by the flexible conductors30.

In the construction of the fuse link |15, shown in Figures l and 2 ofthe drawings, the size of the flexible conductors i1 is vlimited by thesize of inside diameter of the end portions 20 of the sleeve or sheathI9. For the purpose of providing for the use of exible conductors thesize of which is not dependent upon the inside diameter of thehighmelting point sleeve or sheath, the terminal connectors 3i areprovided between the ends of the composite fusible element 21 and theflexible conductors 30. The terminal connectors 3| are somewhat tubularin construction and they may be formedfrom suitable lengths of solid-copper rod. The ends 32 are provided with suitablydrilled apertures forreceiving the ends of the flexible conductors 30. These ends 32 areflattened onto the ends of the flexible conductors 30 in orderto securethem in position and provide electrical contact engagement therewith. Inlike manner the other ends 33 of the terminal connectors 3l are providedwith suitably drilled apertures for receiving the composite fusibleelement 21 formed by the core 28 and the sleeve or sheath 29. Initiallythe core 28 and sheath 29 are of substantially the same length and theinside diameters of the ends 33 are such as to readily permit theinsertion of the ends of the composite fusible element 21.` The ends 33are rence of an arc, that assist in extinguishingfthe same;

In order to house the fuse link 31, shown in Figure 6 of the drawings,or the fuse links shown in Figures 1 and 4 of the drawings, the housingshown generally at 46 in Figures 8 and 9 may be employed. The housing 46comprises a fuse tube41 that is preferably formed of fiber and hasrelatively thick walls, with a longitudinal bore 48 for receiving thefuse link, such as the fuse link 31. The ends of the fuse tube 41 areexternally threaded for receiving in threaded engagement therewith fusetube ferrules 49.- The outer ends 59 of the ferrules 49 are generallycylindrical in shape and are provided with cylindrical apertures 5Itherethrough that are arranged to form extensions of the bore `48. Eachof the cylindrical end portions 50 is provided with a longitudinal slot52 through which the flexible conductors 42 may be positioned forplacing them around the cylindrical portions 50, as is more clearlyshown in Figure 10 of the drawings. It will be observed that a shoulderportion 53 is provided intermediate the ends of the fuse tube ferrules49 for receiving the flexible conductors 42 in contact engagementtherewith. Suitable pins 54 extend through the threaded ends of the fusetube 41 and the ferrules 49, as shown, for holding them securely inplace.

With a view to holding the flexible conductors 42 is position, cableclamp nuts 55 are provided. It will be noted that the inner ends of theclamp nuts 55 are internally threaded for engaging correspondingexternal threads about the inner ends ananas screwed intopositionwiththeexible'ccnductorsIldisposedasshownaroimdthecylindricalends'Ilvoftheferrulesll-,theywillbeclampedbetweentheshoulderportionsIIanidli.

Itisdesirahlethatsomeindicationbeprovidedthatthefuselinktlhssblcwn.Invmost .insulating material such as Bakelite."

cases, when the fuse link I1 blows, a` considerable .volume of gas isgenerated inside of the bore Il ofl the fuse tube Il. Advantage is takenof the 'generation of gas pressure inside oi thefusotulael'lbyprovidingreadilyexpellableplugsv Il in cylindricallyshaped extensions I8 of the clamp nuts Il; The plugs llare preferablyformedofcorkandtheymaybepaintedasuitable color, for example, red, asshown, to more readily provide for determining whether or not the fusedevicelhas operated.

Itwillbelmdersioodthattheiusehousingmaybeplacedinasuitablempportdeviceand that suitable terminals may beprovided for con,- nection to the cylindrical end portions Il oftheclamp nuts IB.

As indicated; considerable pressure may vbe generated within the bore Ilof the fuse tube Il when the fuse device Il blows. If thehousing Ilwerearrangedtobeventedfromoneendonly.it

pute ,relrmdorv tingmstenal, ammaedintotheferruleuformountingthereinanarcing tube il that also'ls formed of a suitable As shown, the mountingplate Il and the arcing tube Il are provided with cooperating ilanges bymeans of which the latter is supported bythe former.

Suitable washers 88, formed of readily frangible material, such asBakeliteff are secured to the mounting plate by screws. (l inoverlapping relation with the arcing tube Il to hold the same inposition until suillcientpressure is generated Y within the housing orsleeve' t! to blow it out of its upper end.

'lhe fuse link t2 is provided with upper and lower terminals l0 and TI.The upperterminal Il is mounted in a supportspider 12 and is securedthereto by a nut ll. The lower terminal 1I is provided with outwardlyextending pins Il that are arranged to carry a liquid director 'il thatis retracted with the terminal 1l o'n blowing ofthe fuse link l2 by acoil tensionspring Il to direct liquid, which illls the housing orsleeve I3 to the level indicatedyinto the varcing chamber would benecessary to provide a support that would have sumcient strength towithstand the reaction applied to the housing; In order to lavoidthisdiiilculty the housing Il is vented att be possible that suillcientpressure wlllgn'ot be generated within the bore 4l to cause the plugsI'I to be expelled. However, this condition is notv often encountered. Y

` Bincethefusetubellisformedofamaterialsuchasbengaseswhichassistinextingulshingthearciormedonblowingofthefuselinkllare levolved'i'rom the bore Il. Theblast action thereby created materially assists in quickly extinguishingthe arc. l

The presentinvention may be embodied in a fuse device of the blastactiorrarc extinguishing type. such as shown in the co-pendingapplication 0f Nicholas J. Cnrd, Serial N0. 470,416, lcd

July 24, 1930, and assigned to the assignee' of this application,n0w.Patent No. 2,091,430,l This embodiment of the invention isillustrated in Figure l2 of the drawings.

As shown, a fuse device, designated generally hy the reference character0I; is provided, that is generally of the type disclosed in thecopendingl application of Conrad, but which is provided with a fuselink, shown generally at Il, that is constructed in accordance with thisinvention. 'Ihe details of construction of the fuse device 0i willbe setforth herein only insofar as is necessary to illustrate the presentinvention.

The fuse device 0i includes a sleeve or housing that may be formed ofglass or Bakelite" and it has as its ends suitable terminal ferruies,one of which is'shown at Il. A vent cap Il is suitably pressed onto theupper end of the ferrule Il and is adapted to be blown oi! on generationof suillcient pressure inside of the sleeve or housing I3, when the fuselink I2 blows. A mounting or tube Il for assisting in extinguishingthearc drawn therein. A ilexible conductor 1l is provided forinterconnectingv the lower terminal 'Il and the lower ferrule oi' thehousing or sleeve Il,

'aswillbereadilyunderstood 'I'he 99er and lower terminals 'III and Ilare arranged to he electrically interconnected by a composite fusibleelement that is shown generally v at Il. The fusible element l0 extendsinto suitable drilled apertures IZ and Il in` the opposing faces of theterminals 'III and 1I.

i relieve the fusible element 80 of the tension Astress that wouldotherwise be imposed by the spring 1l, a tension element Il in the formot a wire composed of a high strength metal, such as a nickel-chromiumalloy, is also provided between the terminala Il and Il withitscorrugated ends Il disposed in suitable apertures I6 and Il therein Witha view to protecting the fusible element Il and the strain element I4 ofthe fuse link t! during installation, and from vibrationafterinstallation, a sleeve Il formed of suitable insulating materialsuch as Bakelite" is provided Y. around them andy around suitablecylindrically shapedporti'ofnsof the terminals lll and 1i, as

Illustrated. The sleeve 8l isA provided with apertures Il adjacent itsends to provide for the escape of liquid therefrom so that no liquidwill remain in engagement with the fusible element Il when the fusedevice 8| is in the upright position for the purpose of avoiding changein its time-current characteristics.

The details of construction of the fusible element Il are shown moreclearly in Figure 14 of the drawings. As there shown, the fusibleelement Il comprises a core li, formed of a suitsleeve or sheath $2,formed of a` relatively high melting point metal such as silver. Theends I3 of the sleeve or sheath 92 extend substantial distances beyondthe ends of the core 0I and these ends are filled with short lengths 94of conductive material formed by a plurality of small strands of wire.If desired, metal plugs may be substituted for the strands of wire u.These plugs would be preferably formed of high heat conducting metalsuch as silver in order to readily conduct the heat generated in thecore Il to the terminals .10 and 1|'.

As indicated hereinbefore, the ends of the fu- In order to.

- 82 and 83 in the terminals. 10 and 1|.

sible element 80 extend into suitable apertures These ends are securedtherein by deforming the adjacent wall of the terminals, as indicated at95 in Figure 13 of the drawings. ende'd tool is provided for deformingthe adjacent terminal material to provide not only for securely holdingthe fusible element 80 in place,

' but also to provide fon electrical contact engagement therewith.

ln a similar manner the corrugated ends 85 of the strain element 84 aresecured in the apertures 86 and 81 of the terminals 10 and 1|. Asindicated at 96 in Figure 13, the adjacent wall of the upper terminal isdeformed onto the corrugated end 85 in the aperture 86.

Since the ends of the composite fusible element 80 are secured to theterminals 10 and 1| by deorming a portion of the Walls thereof, it isdesirable that these ends be so constructed that the deforming operationmay be readily and eiilciently performed, and the desired contactengagement obtained. It is for this purpose that the ends 93 of thesleeveor sheath 92 are preferably filled with the readily deformablestrands 94. Since the core metal 92 may become softened when the fuselink 62 is called upon to conduct current for sustained periods close tothe minimum fusing current, it

is further desirable that some material such as .y

composite fusible element is present for the reason that its operatingtemperature is much lower than that of a silver fusible element whenconducting current close to its minimum fusing current. The majorportion of the heat that is generated in the liquid fuse is conductedaway from it through its end terminals, such as the ferrule 64. It willbe noted that Vthis ferrule is cemented onto the glass housing 63. lt

A suitable blunt is essential foi-satisfactory operation of a liquidfuse that a fluid tight'sealbe maintained to insure that the insulatingproperties of the liquid will remain unchanged so that, on operation, itX will be capable, not only of assisting in extinl guishing the arc, butalso of providing a suitable .comprise a pair of relatively infusibleterminals that are interconnected by fusible means.I A sleeve ofinsulation is ordinarily secured to one of me and other terminal toprotect the link during handling and to provide certain arcextinguishing characteristics. Such links are ar:

gig' terminals and it extends over the fusiblel ranged and constructedso that they are interchangeably adapted to Ibe inserted in practicallyany of the commercial types of fuse tube housings that are now beingsold.

Such a construction is illustrated in Figure l5 of the drawings.4 Asthere shown, the reference character |00 designates, generally, avreplaceable fuse link of the universal type that is provided with a.pair of relatively infusible terminals |0| and |02 that are arranged tobe in-r terconnected by a composite fusible element |03 and astrain-element |04. 'Ihe fusible element S03 may be constructedsimilarly to the fusible element as shown in detail in Figure 14 of thedrawings.

The terminal 0| is provided with a. threaded portion |05 on which isscrewed a cap |06. For certain types of mounting the cap |06 isrequired, while for other types the cap |06 is removed and the link |00is threaded into the cor- -responding socket in the fuse housing. The

for receiving the ends of the fusible and strain elements |03 and |04.The outer surface of the lower portion ||2 is deformed, as shown at ||5and H6 to secure the ends of the fusible and strain elements |03 and |04therein.

The upper end portion |1 of the lower terminal 502 is formed similarlyto the lower portion ||2 of the 'terminal |0| for receiving the otherends of the fusible and strain elements |03 and |04.

The outer surface of,.this portion is likewise de" formed to securelyhold these elements in position. Since the ends of the sheath forming apart of the composite fusible element |03 are iilled with readilydeformable material, such as the fiexible conductors 94, (Figure 14),its ends may be readily deformed as described hereinbefore, so thatproper contact engagement will `be provided with the terminals |0| and|02 and the tin ycore will not be permitted to flow when it is in thesoftened state.

g The lower end ||8 of the terminal |02 is provided with an axiallydrilled aperture I9 for receiving one end of a flexible conductor |20that comprises a plurality of strands of wire. As shown in Figure 17,the opposite sides of the lower end portion ||8 are deformed inwardlyboth longitudinally andV transversely for the purpose of securing theilexible conductor |20 therein and maintaining contact ngagementtherewith under relatively high pressure.

Since this .particular terminal constructionl is illustrated anddescribed in the copending application, Serial No. 138,188, led April21, 1937, by myself and Sigurd I. Lindell, and assigned to the assigneeof this application, a more detailed description will not be set forthherein.

With-a view to providing for connection to an external terminala coneterminal |2| is pressed onto the exible conductor |20. It will beunderstood that the fuse link |00 may be mounted in fuse housings inwhich one or more springs are` provided for biasing the terminals I 0|and |02 apart so that the arc may be rapidly extinguished. In such case,it will be uitderstood that the strain element m relieves thefusible'eiement m or the stress that would otherwise be imposed there'on by the biasing forces.- However, it lwill be understood that the fuselink Ill may be mounted in fuse housings in which springs or otherbiasing means arenotv employed. y I

Since certain further changes may be made in l the foregoingconstructions, and different embodiments of the invention may be madewithout del. Ima fuse, in combinatioma core formed of metal having arelatively low melting point, a

metal' sheath having a relatively high melting point and forming aself-supporting container for Y said core unbonded thereto with at leastone end extending beyond the corresponding end of said core, and metalplug means extending into said one end of said metal sheath forconducting heat away from mid core.

2. In a fuse,in combination, a core formed of metal having a relativelylow melting'point, a metal sheath having a relatively high melting pointand forming a container for said core with at .least'one end lextendingbeyond the corresponding end of -said core, and a flexible conductorformed by a phirality of strands of 4wire extending into said one end ofsaid metal sheath 'and said one end being deformed thereon.

3. In a-fuse link, in combination, a core formed of metal having arelatively low melting point, a

.4 metal sheath having a relatively high melting point and forming acontainer for said 'core with at least one end extending beyond thecorre'- sponding end of said core, a ilexible conductor formed by aplurality of strands of wire extending ametalsleevearmmdsaid oneendofsaidnietal sheath, said metal sleeve and said one end of said metalsheath being deformed about said ilexible conductor.

4. A fuse comprising, in combination. a core formed of metal having arelatively low melting point, a 'metal sheath having a relatively highmelting point and forming. a container for said core of such length thatits ends extend beyond the ends of said core, and conductor meansexrtendinginto said ends of said metal sheath for conducting heataway-from said core.

5. A fuse comprising, in combination, a core formed of metal having arelatively low melting point, a metal sheath having a relatively highmelting point and forming a container for said core of such length thatits ends extend beyond the ends of said core, and a pair of flexibleconductors each 'formed by a plurality of strands of wire extending intosaid ends of said metal sheath and said ends being deformed thereon.

6. A fuse link eomprising, in combination, a core formed of metal,having a relatively low melting point, a metal sheath having arelatively high melting point. and forming a container for said core ofsuch length that its ends extendbeyond the ends of said core, a pair ofnexible obnductors eachli'ormed by a plurality of strands of wire.extending into said ends of said metal sheath and into abutment with theends of said core, and a metal sleeve aroundeach end of said metalsheath, said ends of said metal sheath and said sleeves thereon beingdeformed about said ilexible conductors.

'1. Inafuselink,incombination,ametei core, a self-supporting continuouscontainer surrounding said core formed of metal which alloys therewithon ow of current suillcient to-melt the same, a terminal conductor, anda terminal connector having one end adapted-to receive said containerand said` core and to retain thelatter in the liquid state and the otherend adapted to receive said terminal conductor.

8. In afuselink,\in combination, a metal core, a self-supportingcontinuous container surrounding said core formed of metal which alloysthere with on flow of current sumcient to melt the A same, a terminalconductor, a terminal connector having one end adapted to receive saidcore and container and the otherend adapted to receive said terminalconductor, and closure means between said ends of said terminalconnector adapted to retain said core inthe liquid state.

9. In a fuse link, in combination. a metal core, a yself-supportingcontainer surrounding said core formed of metal which alloys therewithon ilow of current suillcient Vto melt the same, a terminal conductor,and a te connector having one end adapted to receive said container andcore and to retain the latter in the liquid state and the other endadapted to receive said terminal conductor, said one end of saidterminal connector being deformed about said container and said otherend of said terminal connector being deformed about said terminalconductor.

10. In a fuse link, in combination, a core ccmposed principally of tin,a continuous tubular container composed principally .of silversurrounding said core. a flexible conductor, and a terminal connectorhaving one end adapted to receivesaid continuous container andsaid coreand to retain the latter in the liquid state and the other end adaptedto receive said ilexihle conductor.

il. In a fuse link, in combinationI acore com posed principally of tin,a tubular container com;

posed principally of silver surrounding said core,

a flexible conductor, and a terminal connector having one end adapted toreceive said container and said core and to retain the latter in thesame, a pair of flexible conductors, and apair of terminal connectors.each having one end adapted to receive said container and said core andto retain the latter inthe liquid state and the other end adapted toreceive one of said ilexible conductors.

13. A fuse link comprising, in combination, a

core composed principally of tin, a tubular 'container composedprincipally of silver surrounding said core, a pair of ilexibleconductors formed by a plurality of strands of wir'e, and a pair oftubular terminal connectors each having one end adapted to receive saidcontainer and said ocre and to retain the latter in the liquid'state andthe other end adapted to receive-one of said ilexible conductors.

in combination, a j

14. A fuse link comprising, in combination, a core composed principallyof tin, a tubular container composed principally of silver surroundingsaid core, a pair of flexible conductors formed by a plurality ofstrands of wire, a pair of tubular terminal connectors each having oneend adapted to receive said core and container and the other end adaptedto receive one of said' flexible conductors, and closure meansintermediate the ends of each of said terminal connectors.

l5. A fuse link comprising, in combination, a metal core, aself-supporting container surrounding said core formed of metal whichalloys therewith on flow of current suilcient to melt the same, a pairof flexible conductors, a pair of terminal connectors each having oneend adapted to receive said container and said core and to retain thelatter in the liquid state and the other end adapted to receive one ofsaid fiexible conductors, and means mechanically interconnecting saidterminal connectors in addition. to said core and container.

i6. A fuse link comprising, in combination, a metal core, a containersurrounding said core formed of metal which lalloys therewith on flow ofcurrent suflicient to melt the same, a pair of flexible conductors@ pairof terminal connectors each having one end adapted to receive saidcontainer and said core and to retain the latter in the liquid state andthe other end adapted to receive one of said flexible conductors, and asleeve surrounding said container and said terminal connectors. l

i7. A fuse link comprising, in combination, a metal core, a containersurrounding said core formed of metal which alloys therewith on ow ofcurrent sufficient to melt said core, a pair of flexible conductors, apair of terminal connectors each having one end adapted to receive saidcore and container and the other end adapted to receive one of saidflexible conductors, a knurled portion intermediate the ends of each ofsaid terminal connectors, and a sleeve formed of insulating materialsurrounding said container and interiitting with said terminalconnectors at the knurled portions thereof.

i8. In a fuse, in combination, a metal core, a container closelysurrounding and extending beyond the ends of said core and formed ofmetal which alloys therewith on flow of current .suilicient to melt thesame, and means filling the ends of said container for holding said corein place in the molten state.

19. in a fuse, in combination, a metal core, a

container closely surrounding and extending beyond the ends of said coreand formed of metal which alloys therewith on flow of current sufficientto melt the same, readily deformable means liing the ends of saidcontainer for holding said` core in place in the molten state, and arelatively infusible terminal interfitting with and deformed onto eachof said ends of said container.

'20. A fuse linkcomprlsing, in combination, a core formed principally oftin, a cylindrical sleeve vformed principally of silver closely fitting.

lf beyond the ends of the same, a plurality of strands of wire fillingthe extended ends of said sleeve for holding said core in place in themolten state, and a relatively infusible terminal interfltting with anddeformed onto each of said ends of said sleeve.

22. A fuse link comprising, in combination, a pair of relativelyinfusible terminals adapted to be biased apart by a spring; a compositefusible element electrically interconnecting said terminals includingametal core having a relatively low melting point, a metal sleevesurrounding said core and extending beyond its ends into said terminals,and a plurality of strands of wire filling.the ends of said sleeveextending into said terminals; and a strain element extending into saidterminals for relieving said fusible element of stress imposed bythespring tending to separate said terminals, said terminals being deformedonto the ends of said fusible and strain elements. A

23.' A fuse link comprising, in combination, a pair o relativelyinfusible terminals; a composite fusible element electricallyinterconnecting said terminals including a metal core having arelatively low melting point, a metal sleeve surrounding said core andextending beyond its ends into said terminals, and a plurality ofstrands of wire filling the ends of. said sleeve extending into saidterminals; a strain element extending into said terminals for relievingsaid fusible element of stress tending to separate said terminals, saidterminals being deformed onto the. ends of said fusible and strainelements, and a sleeve of insulation interfltting with said terminalsand surrounding said fusible and strain elements.

24. A fuse link comprising, in combination, a pair of relativelyinfusible terminals, a composite fusible element electricallyinterconnecting said terminals including a core composed principally oftin, a sleeve composed principally of silver surrounding said core andextending beyond its ends into said terminals, and a plurality ofstrands of wire filling the ends of said sleeve extending into Ysaidterminals; and' a strain element extending into said terminals forrelieving said fusible element of stress tending to separate said ter-vminals, said terminals being deformed onto the lends of said fusible andstrain elements.

25. A fuse link comprising, in combination, a metal core, aself-,supporting container surrounding said core composed' of metalwhich remains substantially unchanged on flow of current sumcient tomelt said core; a pair of relatively infusible terminals secured to theends of said container and adapted to retain said core in the liquidstate, one having a terminal fitting receiving portion and the otherhaving a conductor receiving portion; and a fiexible conductorsecuredin'said conductor receiving portion.

26. A fuse link comprising, in combination, a metal core, a.containerksurrounding said core formed of metal which alloys therewithon flow of current sufficient to melt the same; a pair of relativelyinfusible terminals secured to the ends of. said container, one havinga' terminal fitting receiving portion and the other having a conductorreceiving portion; a flexible conductor secured insaid conductorlreceiving portion, and' an insulating sleeve secured to said one of saidterminals and extending over the other of said terminals.

27. A fuse link comprising, in combination; a pair of relativelyinfusible terminals, one having a terminal fitting receiving portion andthe -other having a conductor receiving pmtion; a fusible elementelectrically interconnecting said terminals including a corev formed ofmetal having a relatively low melting point and a surroundingself-supporting sheath formed of .metal adapted to allow'with said coreon flow of current sufiicient to melt the same, said terminals beingadapted to retain said core in the liquid state, af

strain element mechanically interconnecting said terminals, and a exibleconductor secured' in said conductor receiving portion.

V28. A fuse link comprising, in combination; a pair of vrelativelyinfusible terminals, one having a terminal ntting receiving portion andthe other having a conductor receiving portion; a fusible elementelectrically interconnecting said terminals including a core formed ofmetal having a relatively low melting point and a surrounding sheathformed of metal adapted to alloy with said core on flow of currentlsumcient to melt the same, a strain element mechanically interconneetingsaid terminals, a exible conductor secured in said conductor receivingportion, said terminals being deformed onto thev respective ends of saidfusible and strain elements and' said flexible conductor, and aninsulating sleeve secured to said one of said terminals and extendingover the other of said terminals and aroimd said' fusible and strainelements.

29. In a fuse link, in combination, a core formed of metal having arelatively low melting point, a metal sheath having a relatively highmelting point and forming a container for said core with at least oneend extending beyond the corresponding end of said core, and a flexibleconductor formed by a plurality of strands of wire secured in said oneend of said metal sheath.

30. In a fuse, in combination, a tin core, a silver sheath forming aself-supporting container for said tin core and extending beyond theends of the same, and metal means carriedI by said silver 4sheath at theends of said tin core for conducting heat away therefrom.

31. In a fuse, in combination, a tin core, a silver sheath forming awif-supporting container for said tin core and extending beyond the endsof the same, and a metal plug withinsaid silver sheath at each end ofsaid tin core for conducting heat away therefrom.

32. In a fuse, in combination, a core formed of metal having arelatively low melting point, a metalsheath having a relatively highmelting point and forming a container for said core and extending beyondthe ends of the same, and metal means having relatively high thermalcapacity and heat conductivity carried by said sheath at the ends ofsaid core for conducting heat away therefrom and limiting thetransmission of heat thereto.

33. In a fuse, in combination, a core formed of tal having a relativelylow melting point, a

meial sheath having a relatively high melting a terminal tting receivingportion and the other having a conductor receiving portion; a fusibleelement electrically interconnecting said terminals including a coreformed of metal having a relatively low melting point and a surroundingsheath formed or mem adapted to alloy with said core on sow 75 or'current sumcient to meu the same, a strain velement mechanicallyinterconnecting said tersaid fusible and strain elements.

35. A fuse link comprising, in combination; a pair of relativelyinfusible terminals, one having a terminal fitting receiving portion andthe other having a conductor receiving portion; a fusible elementelectrically interconnecting saidterminals including a tin core and asurrounding silver sheath, a strain element mechanically interconnectingsaid terminals, a flexible conductor secured in said conductor receivingportion, and an insulating sleeve extending between said terminals andaroimd said fusible and strain elements.

36. In a fuse, in combination, a core formed of metal having arelatively low melting point, a metal sheath having a relatively highmelting point and forming a container for said core and extending beyondthe ends of the same, metal plus means nlling the ends of said sheathfor conducting heat away from said core, and a relatively infusibleterminal intertltting with and deformed onto each end of said sheath andthe metal plug means therewithin.

37. In a fuse, in combination, a core formed of metal having arelatively low melting point. a metal sheath having a relatively highmelting point and forming a container for said core, and terminal meansat the ends ofvsaid sheath at least one of which includes flexibleconductor means and metallic sleeve means cooperating with said sheathand flexible conductor means whereby the same are mechanically andelectrically interconnected.

the element and is capable of alloying with the.-

tin core when heated to its melting temperature, thereby increasing theresistance of the element so that it ruptures once the alloying actionis initiated.

40. In a fuse, in combination, a core formed of metal having arelatively low melting point, a sheath formed of metal having arelatively high melting point surrounding said core and extending beyondthe ends if the same, and an imperforate plug formed of metal having arelatively high melting point filling each end of said sheath andengaging the ends of said core for conducting heat away therefrom. V

41. In a fuse, in combination, a core formed of metal having arelatively low melting point. a sheath formed of metal having arelatively high melting point surrounding said core and extending beyondthe ends of the saine, an imperforate plug formed of metal having arelatively high melting point lining each end of said sheath andengaging the ends of said core for conducting heat away therefrom, and arelatively infusible terminal inter'fltting with and deformed onto eachend of said sheath.

silver sheath surrounding said core and extend-- ing beyond the ends ofthe same, and 'a silverA plug illling each end of said sheath andengaging the ends of said core for conducting heat away therefrom.

44. a fuse, in combination, a tin core, a silver sheath surrounding saidcore and extending beyond the ends oi' the same. an imperforate plugformed of metal having a relatively high melting point lling each end ofsaid 1 sheath and engaging the ends of said core for conducting heataway therefrom, and a relatively infusible terminal interiltting withand deformed onto each end o! said sheath.

HUGH A. TRIPLETT.

